Thickening fluid the secret of stab-proof clothing.
this is a non-newtonian fluid. It works very much like Oobleck, cornstarch in water. See http://en.wikipedia.org/wiki/Non-Newtonian_fluid for a long list of mixtures that have similar properties at various strength. In this military grade non-Newtonian fluid, cornstarch is replaced with silica, water is replaced with polyethylene glycol. Watch at time mark 4:43 closely and notice that the free hanging bottle did not drop. It means that the liquid reacts to force as low as Earth's gravity. He had to hold the bottle and free the rod with less force than gravity.
The video does not tell how to keep this solution in liquid form over time. It will probably lose its shielding property when the liquid dry out.